Introduction
The cervical spinous process and transverse process, which are the vital osseous marks of the cervical static palpation, play important roles in cervical spinal manipulation.1 In clinical spinal manipulation practice, the deviation of spinous process is regarded as very important objective evidence of minor misalignments of joints, such as the type I and II atlantoaxial rotatory subluxation and atlantoaxial rotatory fixations.2 The diseases of the atlantoaxial joint have been a topic of general interest in clinical research owing to the high risk of myelopathy and life-threatening neurologic injuries.3, 4 Cervical spinal manipulation is one of the nonsurgical treatments to treat the diseases of minor misalignments of joints by manual therapists, chiropractors, physical therapists, etc.5, 6, 7 The function of cervical spinal manipulation to correct the atlantoaxial joint is regarded as manipulative reduction.8, 9, 10 In clinical practice, the deviation of spinous processes, which is manually palpable by therapist, is often used to determine atlantoaxial joint derangement.11, 12, 13 However, the structure and function of atlantoaxial vertebral anatomy are quite complex, which results in misdiagnosis and confusion in clinical practice and interventions.14, 15 To improve the accuracy in treatment of minor misalignments of joints, a comprehensive research study has been performed on the anatomical structure of axis to delineate and provide the anatomical basis for accurate positioning of the cervical static palpation.